Backup Strategy question from stupid Newbee

Sorry for my ignorance, but as a newbee I'm totally confused about what I've found by searching the forum (or perhaps simply too stupid to understand)

- I want to make daily backups from my internal disks C: and D: onto an external 500GB drive
- In case of a desaster, I want to be able to restore OS and data, so I choose "backup computer"
- In order to reduce backup time I choose differential backups on each weekday and a full backup on sunday, which means I start on a sunday, let TI make 6 differentials before a new full backup and could restore my PC status of the last 7 days.

Now, how and when does TI erase the old/existing full backup on a sunday - before or after having done the new full backup? Or in other words: what happens in case of a power failure/earthquake/kid pourring coke over my pc? Am I left with no backup at all or is there ONE full back always available?

Sorry, if this is stupid basic to all of you, but I've really got stuck here...

If using Backup Locations in ATI, and doing full backups, then the oldest backup is deleted to accomodate the preet limits - this happens after/B] the backup is made. E.g., if you have a limit of 10 backups, then after the 11th is made, ATI will delete the oldest (so be sure to leave room for that extra backup). This ensures that, incase something goes wrong with the backup you don't end up deleting a perfectly good backup.

If you're doing diffs/incs, then when the limit is reached, ATI will consolidated the oldest set of files into a single full file, and then if necessary to meet limits will delete the oldest full backup.

... I'm not sure about what I am doing wrong here, but I'm constantly getting into the same problem (was just checking my posts here, the first one is from december 2006!), and still my ATI doesn't do what I want it to do:

On top of my wishlist is the following: Please, make one full backup, then every day make 1 differential backup, do this for 6 days, after that, please, make a new full backup...

ATI makes one full back up and then each day one differential backup, since 10 days, filling up my backup disk...

This really drives me crazy, 'cause I want my backup software to be a help and not a problem. I'm about to look for another backup solution/software soon...